Chloropicrin-propargyl bromide fumigant



United States Patent Ufliee 3,025,246 Patented lvlar. 20, 1952 3,026,246CHLOROPICRiN-PROPARGYL BROMIDE FUMIGANT Charles R. Youngson, Long Beach,and Cleve A. I. Goring, Garden Grove, Calif., assignors to The DowChemical Company, lvfidland, Mich., a corporation of Delaware NoDrawing. Filed Oct. 30, 1959, Ser. No. 849,768 9 Claims. (Cl. 167-39)The present invention relates to fumigant compositions and isparticularly concerned with a new fumigant composition and an agronomicpractice for improving the ability of soil to support plant growth.

It is an object of the present invention to provide a new fumi antcomposition. A further object is to supply a new agronomic practice andcomposition for improving plant growing properties of soil and theability of soil to support the growth of crops. Another object is theprovision of a new method and composition for improving the emergence,seedling growth and the harvest of crop plants. A further object is theprovision of a new method and composition for treating soil to obtainimproved controls of soil-dwelling invertebrate organisms such as Wireworms and nematodes. An additional object is the provision of a newmethod and composition for treating soil which will accomplish thestimulation of the growth of crops. Other objects will become apparentfrom the following specification and claims.

The new fumigant composition of the present invention comprises aboutone part by weight of chloropicrin in admixture with from about 0.05 to3 parts by weight of propargyl bromide. While this compositionadvantageously may be employed in many types of fumigation operations,it conveniently adapts itself to the treatment of soil or other growthmedia to improve the ability of the soil to support plant growth and tobenefit the plants grown in the treated soil. Such practice protects theplants from the ravages of soil-dwelling invertebrate rganisms whichattack their roots and improves the growth and harvest of crop plants.It has also been found that the treatment accomplished changes in thesoil which stimulate the growth and improve the growth characteristicsof crops grown therein. It is among the advantages of the presentinvention that the toxicants in the mixture appear to be mutuallyactivating so that a greater than additive, or synergistic, result isaccomplished as regards the efiect on plant growing properties of thesoil and control of insect and other undesirable organisms andparticularly inverterbrates such as wire worms and nematodes.

The composition comprising the mixture of toxicants is sufficientlyincreased in efiectiveness so as to permit the effective utilization ofreduced amounts of chloropicrin and of propargyl bromide on soil and theobtaining of crop yields and controls of soil-dwelling organisms whichare much superior to those obtained when either of the constituents ofthe mixture is employed alone. An additional advantage is that thesereduced effective dosages of the mixture of toxicants materially reducethe hazards of soil residues. Thus, the practice of the presentinvention provides a very desirable economic advantage for theagriculturist.

Chloropicrin and propargyl bromide are mobile liquids which boil at 112C. and 8890 C. at atmospheric pressure, respectively. Mixtures of thecompounds are somewhat soluble in many organic solvents and of lowsolubility in water and are adapted to be conveniently distributed insoil. It is among the advantages of the present invention that mixturesof these compounds, while sufiiciently persistent to accomplish thedesired effect upon the soil and upon the soil inhabiting organisms,dissipate in a reasonable period of time. Still another advantage isthat mixtures of these compounds permeate soil for a distance of severalinches from the point of application depending upon the temperature,organic content, moisture content, compactness and physical consistencyof the soil or growth media.

In carrying out the improved agricultural practice of the invention, thechloropicrin and propargyl bromide may be mixed together and suchmixtures employed directly in parasiticidal quantities for the treatmentof soil. However, the present invention also embraces the employment ofgaseous, liquid or dust compositions containing the mixture of toxicantsand for any fumigant purpose where the composition is useful. Thus, themixture of toxicants may be dissolved in a suitable liquid carrier toprovide compositions adapted to be distributed in soil. Such liquidcompositions may also be employed to fumigate the surfaces of certainfruits, vegetables and grains where these products tolerate thefumigation action. Similarly, the chloropicrin and propargyl bromide maybe dispersed on or in a granular or finely divided solid carrier toprovide compositions adapted to be distributed in soil or employed asconcentrates and subsequently diluted with additional inert carrier toproduce the ultimate treating compositions. In a further mode ofoperation, the chloropicrin and propargyl bromide may be blended with asuitable surface-active dispersing agent with or without one or moreliquid carriers to provide concentrates suitable for dispersion in waterto prepare soii treating compositions in the form or" aqueousdispersions or emulsions.

The compositions of the invention may be prepared in any suitablefashion. Since chloropicrin and propargyl bromide are miscible in allproportions, compositions without carriers may be prepared by simplemixing of the components at ordinary temperatures. in the preparation ofcompositions containing a liquid organic carrier, chloropicriu andpropargyl bromide are thoroughly mixed in the liquid organic carrier atconvenient temperatures. Suitable organic carriers include liquidaliphatic and aromatic hydrocarbons such as toluene, xylenes, naphthasand hydrocarbon mixtures derived from the distillation of petroleum orcoal, and other organic solvents such as acetone. For some fumigationoperations such carriers as carbon tetrachloride or ethylene dichloridemay be employed. In general, it is preferred to avoid liquid carriershaving such low flash points as to constitute a fire hazard or such highboiling points as to leave undesired residues after use of thecompositions. Depending upon the concentration of the mixture oftoxicants, such augmented compositions are adapted to be distributed inthe soil or otherwise, or employed as concentrates and subsequentlydiluted with additional carrier to produce the ultimate treatingcompositions.

In a preferred embodiment of the invention, selected petroleumdistillates are employed as liquid carriers. Petroleum distillates usedin such embodiment are carefully fractionated portions boiling almostentirely under 406 F. at atmospheric pressure and having a hash pointabove about F. These fumigant compositions are characterized byexcellent penetrating properties and by low fire hazard to the shipperand user.

In preparing dispersible concentrate compositions, chloropicrin andpropargyl bromide components are mixed in the propontions previously setforth together with a surface-active dispersing agent soluble in thecomposition with or without the further addition of a liquid organiccarrier. The surface-active agents are usually employed in the amountfrom about 1 to 20 percent by weight of the combined weight of thetoxicant mixture and surface-active agent. Suitable surface-activedispersing agents include polyoxyalkylene derivatives of alcohols,phenols and organic acids; oil-soluble petroleum sulfonates;polyoxyethylene derivatives of glycerol; glycols; and the like.

In compositions in which chloropicrin and propargyl bromide aredispersed on or in a granulated or finely divided solid carrier, thecomponents may be added directly to the solid carrier with mechanicalmixing. Alternatively, the components may be combined with one or moreof the aforementioned liquid organic carriers and the resultingcompositions admixed with the solid carrier. Suitable solid carriersinclude silica gel, woodfiour, fullers earth, chalk, gypsum and thelike.

In formulating the compositions, effective proportions of the activetoxic ingredients range from about one part by weight of chloropicrin toabout 0.05 to 3 parts by weight of propargyl bromide. Having obtainedthe active mixture, it is necessary to add an effective amount of saidmixture to the carrier composition in order to obtain the desiredsynergistic effect. The concentration of the mixture of toxicants inorganic solvent compositions employed to supply the desired dosage isgenerally from 7 about 1010 85 percent by weight. With aqueouscompositions, the required dosage is generally supplied withcompositions containing from about 1 to 50 percent, althoughconcentrations of 0.0002 percent by weight may be conveniently employedin irrigation treatments of soil. In compositions wherein the activemixture is dispersed on the solid carrier, it is generally desirable toemploy from about 1 to about percent by weight of the above mixture ofactive ingredients in the finished solid composition. With high capacitycarriers, such as silica gel, the active ingredients may amount to 50percent by Weight or more of the solid composition. In any case, it isdesirable to employ sufficient quantities of the solid carrier so thatthe liquid composition is sorbed to provide a free-flowing solidmixture. In compositions to be employed as concentrates, the toxicantmixture oftentimes is present in a concentration of about 5 to about 95percent by weight.

The soil may be treated with the toxicant mixture or a compositioncontaining the mixture of toxicants in any suitable fashion. With liquidcompositions, good results have been obtained by depositing the activefumigant mixture at regular intervals beneath the surface of the soil.Such deposition may be accomplished readily by automatic machinery or byhand-operated apparatus.

' Thus, the active composition may be sprayed or otherwise deposited ina furrow which is subsequently closed to keep the active agents in thedesired zone of the soil to be treated. Alternatively, the liquidcompositions may be injected into the soil at predetermined intervals.In any case, the active composition is usually deposited at a depth offrom about 4 to 18 inches below the soil surface.

In row treatments it is advantageous to place the fumigant compositionat least 12 inches below the surface of the seed bed and to seal in thefumigant by listing the soil or by other suitable means such as ringrollers or press sealers attached behind the applicator. In overallapplications with chisel-type applicators, the fumigant composition maybe applied in uniform treatments 1 to 112 inches apart at a depth of 6to 8 inches. With plowsole applications, it is desirable to employ about8 inches spacing between the furrows and to spray or otherwise introducethe fumigant composition so as to cover the bottom of the furrow. Whereinjection of the active composition at intervals is employed, goodresults are obtained when injecting at intervals of from 3 to 12 inches,although somewhat greater intervals may be employed in certain cases. Inthe above operations, it is desirable i to apply the fumigantcomposition after the soil has been worked into seed bed condition andwhen the soil temperature is above F. and the soil moisture content issufiicient for seed germination.

In another mode of operation, the fumigant composition in emulsifiableform may be dispersed in water employed to irrigate the soil. In thismethod, the amount of water may be varied in accordance with theporosity and water-holding capacity of the soil in order to obtain thedesired depth of distribution of the toxicant mixture.

The amounts of the chloropicrin and propargyl bromide compostion to beemployed will vary depending upon such factors as the type and conditionof the soil, the varieties and growth stages of soil pests to becontrolled and the particular crop to be planted thereafter. Theessential criterion is to employ an amount for accomplishing the desiredeffect upon the soil-dwelling invertebrate organisms and the plantgrowing properties of the soil. In general, good results are obtainedwhen the mixture of toxicants is distributed in growth media to a depthof from 4 to 12 inches at a dosage of at least one pound per acre. Infield applications, the mixture of toxicants is usually introduced intothe soil at a depth of about 6 inches and at a dosage of from 1 to 50pounds per acre. Where compositions embodying a liquid or solid carrierare used, the amount of composition is adjusted to distributesubstantially the above decribed amounts of the active toxicant mixtureper acre. The required amount of the toxicant mixture in the soil mayconveniently be supplied per acre treated in from about 10 to 100gallons of organic solvent carrier, in from 10 to 162,000 gallons ormore of the aqueous carrier or in from about 50 to 1000 pounds or moreof the solid carrier.

In one embodiment of the invention, the treated soil is planted with thedesired crop plant following the distribution of the toxicant compoundsin the soil. Where minimum dosages of the toxicant compounds aredistributed in soil, the treated soil may be immediately planted withthe desired crop. Following the distribution of larger dosages of thetoxicant compounds, it is desirable that any planting operation not becarried out for a period of from several hours to several days, theexact period depending upon the concentration of the toxicant compoundsin the soil and the resistance of the species concerned to thecompounds. Where the mixtures of toxicant compounds is employed for thetreatment of the soil adjacent to the root system of established plantshaving resistance to the compounds and in side dressing operations, theexisting vegetation is not unfavorably affected by minimum effectiveconcentrations of the toxicant compounds temporarily present in thesoil.

Illustratively, beneficial results were obtained by injecting acetonesolutions of the active fumigants of the present invention into sandyloam soil naturally infested with root-knot nematodes.

Specifically, acetone solutions of chloropicrin and propargyl bromidewere prepared at concentrations suflicient to provide desired dosages inpounds per acre foot by application of 0.1 milliliter of said solutionsto grams of soil. The infested sandy loam soil was placed in 4 ouncescalable jars and thereafter treated with the foregoing solutions byinjection. The jars of treated soil were then sealed and set aside forone week at about Following the one week interval, the containers wereunsealed and the soil allowed to aerate for one week and thereafterplanted with three cucumber seeds. During the subsequent growing period,no adverse effect upon the growth of the seedlings, attributable to thepresence of residual fumigant was observed. After the cucumbers had beenallowed to grow for a sufiicient period of time that root-knotnematodegalls were develop in the various containers, the cucumber roots werewashed, inspected for gall formation, and noted in the following manner:

TABLE I Toxicity of F umigants t Root-Knot Nematodes [Percent Control ofNematodes] Pounds per Acre Foot chloropicrin Propargyl Bromide 12.5 1n 8i 4 a In a manner identical to that described above, additional testswere run for various mixtures of chloropicrin and propargyl bromide atdosages specified in the following table. The actual control resultsobtained from these tests are compared with expected control computed inaccordance with the graphical approximation method for similar jointeffect of ingredients of the mixture, as presented in Wadley, TheEvidence Required to Show Synergistic Action of Insecticides and a ShortCut in Analysis, United States Department of Agriculture, PublicationEP-223, June 1945.

The concentrate compositions as above described are adapted to bedispersed in water to produce aqueous compositions having very desirablewetting and penetrating properties. The latter aqueous compositions andthe above described solvent fumigant compositions are adapted to beemployed to treat soil and to distribute the mixture of toxicantstherein in effective concentrations. The use of such fumigantcompositions gives results comparable to those tabulated above.

The compositions of the present invention as hereinbefore described aredispersed in water to produce a material containing about pounds of therespective toxicants per 200 gallons of ultimate mixture. The dispersionwhile under agitation, is metered into irrigation water at the pumpoutlet at the rate of 2 gallons per 1000 gallons of irrigation water.The water is in a state of turbulent flow as it comes from the pumpwhich provides for the thorough mixing of the fumigants therein. About 2acre inches of irrigation water is applied per acre to land heavilyinfested with wire worms and root-knot nematodes to accomplish a wettingof the soil to a depth of about 12 inches. Two weeks after thetreatment, the soil is planted. In a check operation, adjacent butsimilarly infested soil is also planted. Eight weeks after seeding, theplots are inspected and representative plants lifted from the soil andtheir roots examined for evidence of wire worm and nematode attack. Theexamination indicates a commercial control of both soil organisms in thetreated soil with severe infestation in the check plots.

Additionally, fumigant mixtures containing from one part by weight ofchloropicrin and from about .05 to 3 parts by weight of propargylbromide are admixed with the following adjuvants: (1) finely dividedinert solids, such as silica gel and the like; (2) emulsifying anddispersing agents such as dimeric alkylated aryl poiyether alcohols,alkyl aryl suifonates and the like; and (3) low boiling petroleumhydrocarbon distillates, such as Stoddard solvent, Standard Thinner 250,and the like. The amount of such adjuvants employed in thesecompositions may vary from 50 to 99 weight percent for the finelydivided inert solids, from 1 to 20 weight percent for the emulsifyingand dispersing agents and from 15 to weight percent for the petroieumdistillates. Compositions obtained with the petroleum distillates haveat least a flash point greater than 100 F.

The foregoing examples are not to be construed as limiting. Further,various modifications may be made in the present invention withoutdeparting from the spirit and scope thereof and the invention is limitedonly as defined in the claims.

We claim:

1. A fumigant composition comprising, as active toxic ingredients, about1 part by weight of chloropicrin and from about 0.05 to 3 parts byweight of propargyl bromide, the active toxic ingredients of saidcomposition being mutually activating.

2. A fumigant composition comprising a carrier and dispersed therein, asactive toxic ingredients, about 1 part by weight of chloropicrin andfrom about 0.05 to 3 parts by weight of propargyl bromide, the activetoxic ingredients of said composition being mutually activating.

3. A composition comprising as active toxic ingredients, about 1 part byweight of chloropicrin and from about 0.05 to 3 parts by weight ofpropargyl bromide in intimate admixture with an inert carrier.

4. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a finely divided inert solid.

5. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a petroleum distillate.

6. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a surface-active dispersing agent.

7. A fumigant composition which comprises an aqueous dispersion of thecomposition claimed in claim 3, wherein the active toxic ingredients areadmixed with a surface active dispersing agent and the mixture of activetoxic ingredients are present in the amount of at least 0.0002 percentby weight.

8. In the practice of agricultural economy, the process which comprisestreating soil with a parasiticidal dosage of a composition comprisingabout 1 part by weight of chloropicrin and from about 0.05 to 3 parts byweight of propargyl bromide.

9. In the practice of agricultural economy, the method which comprisestreating soil with a parasiticidal dosage of a composition comprising asactive toxic ingredients about l part by weight of chloropicrin and fromabout 0.05 to 3 parts by weight of propargyl bromide in intimateadmixture with a petroleum distillate.

References Cited in the file of this patent UNITED STATES PATENTS2,794,727 Barrons June 4, 1957 OTHER REFERENCES Frear: Chemistry ofInsecticides, Fungicides and Herbicides, 2nd ed., 1948, p. 111.

1. A FUMIGANT COMPOSITION COMPRISING, AS ACTIVE TOXIC INGREDIENTS, ABOUT1 PART BY WEIGHT OF CHLOROPICRIN AND FROM ABOUT 0.05 TO 3 PARTS BYWEIGHT OF PROPARGYL BROMIDE, THE ACTIVE TOXIC INGREDIENTS OF SAIDCOMPOSITION BEING MUTUALLY ACTIVATING.